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Climate: Greenland ice loss accelerates

The Greenland ice sheet.  IMAGE COURTESY NASA.

New measurements help pinpoint geographic variations and identify different factors in ice sheet changes

By Summit Voice

SUMMIT COUNTY — Using nifty new high tech tools, German researchers say they’ve been able to pinpoint places where the Greenland ice sheet is losing mass — and found significant geographical variations in the rate of loss.

Their overall findings suggest that ice loss during the past 10 years due to melting and iceberg calving is unusually high compared to the last 50 years.

The research was undertaken in the framework of the Helmholtz Climate Initiative REKLIM of the Helmholtz Association and the EU ice2sea project. The scientists said they observed a complex pattern of ice loss that changes from year to year, based on weather conditions in different areas of Greenland.

Combining measurements taken from two different satellites, including precise laser altimeter measurements, as well as meteorological data showing ice accumulation and glacier discharge, the scientists said the melting Greenland ice sheet is contributing about 0.7 millimeters per year to the currently observed total sea level rise of about 3 mm per year, increasing at about 0.07 millimeters per year.

The detailed assessment enabled the researchers to determine to what degree melting, iceberg calving and fluctuations in rainfall have on the wasting of the ice sheet.

For example, an unusually large increase in ice loss after 2005 was partly due to heavy snowfall the previous years, said  GFZ scientist Ingo Sasgen, who led the study. “Similarly in eastern Greenland, in the years 2008 and 2009 there was even a mass increase,” Sasgen said.

As the researchers were able to show, this was not due to decreased glacier velocities, but because of two winters with very heavy snowfall. Meanwhile, the loss of ice mass continues.

“We now know very well how calving glaciers and melting contribute to the current mass balance, and when regional trends are largely caused by rainfall variations. And we also know where our measurements must be improved,” he said.

One such area is north-western Greenland, where the comparison of data indicates an abrupt increase in the calving rate, which was inadequately detected by the radar data.

The scientists want to find out what causes this increase and if it’s continuous or periodic. To do that, long-term studies using the gravity data from GRACE satellite mission is needed.

The study will be published in the June 1 issue of Earth andPlanetary Science Letters.

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